Acceleration sensor

Abstract

An acceleration sensor includes a frame having a hollow space at an inside thereof, four beams extending from the frame to the hollow space, four plummets connected to ends of the four beams, and four sensing units provided on the four beams. One ends of the beams is connected to portions of the frame opposite to each other with respect to the hollow space. The two plummets face each other across the center of the hollow space. One ends of the other two beams are connected to portions of the frame opposite to each other with respect to the hollow space. The other two plummets face each other across the center of the hollow space. This acceleration sensor reduces variations and temporal changes in its sensitivity.

1 . An acceleration sensor comprising:
 a frame having a hollow space at an inside thereof;   first, second, third, fourth, fifth and sixth beams extending to the hollow space, the first, second, third, fourth, fifth and sixth beams having one ends and other ends opposite to the one ends, the one ends being connected to the frame;   first, second, third, and fourth plummets connected to the other ends of the first, second, third, and fourth beams, respectively; and   first, second, third, and fourth sensing units disposed at the first, second, third, and fourth beams, respectively,   wherein each of the one ends of the first and second beams are connected to respective one of portions of the frame opposite to each other with respect to the hollow space,   wherein the first plummet faces the second plummet across a center of the hollow space,   wherein each of the one ends of the third and fourth beams are connected to respective one of portions of the frame opposite to each other with respect to the hollow space, and   wherein the third plummet faces the fourth plummet across the center of the hollow space,   wherein the one end of the sixth beams is connected to the frame,   wherein the other end of the fifth beams being a free and,   wherein the fifth beam is provided between the first beam and the sixth beam.   
     
     
         2 . The acceleration sensor according to  claim 1 ,
 wherein the first, second, third, and fourth plummets has projections,   wherein the projection of the first plummet faces the projection of the second plummet across the center of the hollow space, and   wherein the projection of the third plummet faces the projection of the fourth plummet across the center of the hollow space.   
     
     
         3 . The acceleration sensor according to  claim 1 , wherein, an area of a gap in the hollow space that are not occupied by any of the first, second, third, and fourth plummets and the first, second, third, and fourth beams is smaller than a total area of upper surfaces of the first, second, third, and fourth plummets. 
     
     
         4 . The acceleration sensor according to  claim 1 , wherein a shape of the first, second, third, and fourth plummets all combined is similar to a shape of the hollow space. 
     
     
         5 . The acceleration sensor according to  claim 1 , wherein thicknesses of the first, second, third, and fourth beams are smaller than a thickness of the frame and thicknesses of the first, second, third, and fourth plummets. 
     
     
         6 . An acceleration sensor comprising:
 a frame having a hollow space at an inside thereof;   first and second beams extending to the hollow space along a predetermined axis, the first and second beams having one ends and other ends opposite to the one ends, the one ends being connected to the frame;   first and second plummets connected to the other ends of the first and second beams, respectively; and   first and second sensing units disposed at the first and second beams, respectively,   wherein each of the one ends of the first and second beams are connected to respective one of portions of the frame opposite to each other across a center of the hollow space, and   wherein the first plummet faces the second plummet along the predetermined axis.   
     
     
         7 . The acceleration sensor according to  claim 6 , wherein, an area of a gap in the hollow space that are not occupied by any of the first and second plummets and the first and second beams is smaller than a total area of upper surfaces of the first and second plummets. 
     
     
         8 . The acceleration sensor according to  claim 6 , wherein a shape of the first and second plummets both combined is similar to a shape of the hollow space. 
     
     
         9 . The acceleration sensor according to  claim 6 , wherein thicknesses of the first and second beams are smaller than a thickness of the frame and thicknesses of the first and second plummets. 
     
     
         10 . The acceleration sensor according to  claim 1 , further comprising a fifth sensing unit disposed at the fifth beam.